Square wave generator



Jan. 2, 1951 R. L. HAYNES SQUARE WAVE GENERATOR Filed April 19, 1946 A, INVENTOR. Kofierf L. 1527064 BY A ea ATTORNEY Patented Jan. 2, 1951 UNITED STATES SQUARE WAVE GENERATOR Robert L. Haynes, Indianapolis,- :Ind.,. assignor to;

Radio Corporation of America, a corporation of Delaware ENTE. 0. RF! i Application Apr-i119, 1946, Serial No. 663,419 1 2 Claims.

Thiszinvention relates to square wave genera tors 10f .-.the .type which are energized from an ordinary commercial alternating 'potentialsourcea andzfunctionto.produce anoutput current hav inga .squarezrwave. shape Such a generatoris useful for. various .purposesx lnf the form herein disclosedz. it .has-.special application to cases where; a current .of. substantially .constantyalue is requiredx. 1

the audible range. For this reason, it has been customary to heat such a lamp by direct current or by alternating current having a frequency outside the audible range. This frequently involves special types of apparatus such as motor generators or the like and is subject to various other types of inconvenience.

In accordance with the present invention, these various difliculties are largely avoided by the provision of an improved generator which functions to produce an alternat ng potential which is substantially square so that it changes almost instantly from its plus to its minus value and maintains constant and equal values throughout its positive and negative half cycles. To this end, a pair of push-pull electron discharge devices of the gaseous conduction type (RCA 2050) have an inductance of relatively large value connected in their common lead and have their grid potentials so controlled as to time very accurately the beginning of each half cycle of the output voltage. Under these conditions, the ripple in the output voltage is decreased to a point where it is not objectionable.

The principal object of the invention is to provide an improved generator and method of operation whereby the value of a square wave potential is maintained constant and equal during its positive and negative half cycles. Additional objects are the provision of an improved circuit for controlling the grid potentials of a pair of push-pull connected gaseous conduction devices, and the provision of improved means for stabilizing the operation of push-pull circuits.

The invention will be better understood from the following description considered in connection with the accompanying drawings and its scope is indicated by the appended claims.

The single figure of the drawing is a wiring diagram of the improved square wave generating circuit.

This circuit includes an input transformer I which has a primary winding lliandfa plurality.i.-; of secondary-windings: I2,- 13; and 14; .Itzalsow includes anoutput transformer l5 having a primarywinding, lfii'andza-a secondary windingx. il l from zwhichxcurrent' is suppIiedtO: a load device shownasa resistorid." Current is supplied from a the secondary; winding ;l 2 for heating the 1 cath-.- ode it of a gaseous;:conduction. electron dis-is charge-:device; l 3 andz-from. :the secondaryrwinda mgr-i3; for..;heatingc. the cathode-.20 -'of,;a'; similar1 device 21;

Connected across one halfthesecondaryiwind-ar inglei-area resistorRi. of. l0,000 ohmstand--a re sistoryRz. of 100.000 ohms-.1: similarlyzconnected-i:

across the other half of the secondary winding M are a resistor R3 of 100,000 ohms and a resistor R4 of 10,000 ohms. Capacitors C1 and C2 are connected in shunt to the resistors R1 and R3 respectively. With these connections, the time required for the control grid 22 to become sufliciently positive to unblock the device [9 is determined by the voltage drop of the resistor R1 and the charging rate of the capacitor C1 which may have a capacity of 0.1 microfarad. The potent al of the control grid 23 of the device 2| is similarly controlled by the voltage drop of the resistor R3 and the capacitor C2 which may have a capacity of 0.1 microfarad. v

Connected between the midpoint terminals of the secondary winding l4 and the primary winding I6 is an inductor L. If th s inductor could be made infinitely large, it would resist changes in the output currents of the devices 19 and 2| to such an extent that the current flowing through it would be constant and would be flowing half the time through the device l9 and half the time through the device 2!. Thus the requirements for constant output voltage are (1) that the value of the inductor L be large, (2) that the devices I9 and 2| conduct alternatively and never at the same time, and (3) that the transformer l5 be an ideal transformer.

It has been determined that with a value of I! henrys for the inductor L there is a reduction of about 10 decibels in the ripple component of the light output of a 10 volt, 5 ampere exciter lamp, and that increasing the value of this inductance to a value of henrys reduces the ripple in such light output by about 20 decibels. Ihis shows a decided improvement in the con stancy of the output voltage.

The problem of so timing the starting of; current through the devices [9 and 2| so that they each conduct current only during successive half cycles which are separate and distinct from one another is solved by the R101 and R302 networks which allow the grids 22 and 23 to become sufficiently positive to unblock the devices 19 and 2| only at a predetermined point in the half cycles of the alternating potential applied to the primary winding II.

It has been found that transformers of the ordinary radio power type are capable of performing satisfactorily in the circuit herein disclosed.

What the invention provides is a circuit which is energized from a conventional alternating potential source and functions to deliver an alternating potential having a substantially constant value and a square wave shape.

I claim as my invention:

1. The combination of a pair of gaseous conducti'on devices each having grid and anode circuits, an output means connected between the anodes of said devices and provided with a terminal intermediate its ends, four resistor sections connected between the cathodes of said devices, an inductor connecting said intermediate terminal to said cathodes through difierent pairs of said resistor sections, and a pair of resistancecapacity networks each including a different one of said resistor sections and each connected in a different one of said grid circuits.

2. A square wave generator including a transformer winding having end terminals and a midpoint terminal, first and second gaseous conduction devices each having an anode, a cathode and a control grid and each having its cathode connected to a difierent one of said end terminals,

an anode circuit for each said device, an inductor connected to said mid-point terminal and common to the anode circuits of said devices, and a pair of resistance-capacity networks each having its input connected between said midpoint terminal and a difierent one of said end terminals and each having its output connected to a difierent one of said control grids, the values of the constants of said networks being such as to time the starting of current through said devices at predetermined points in the half cycles of the alternating current potential of said winding.

ROBERT L. HAYNES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,003,992 Cockrell M June 4, 1935 2,021,888 Dawson Nov. 26, 1935 2,080,250 Bedford May 11, 1937 2,097,297 Meir Oct. 26, 1937 2,148,053 Balmford Feb. 21, 1939 2,154,284 Rose Apr. 11, 1939 2,210,690 Slepian Aug. 6, 1940 2,231,499 Gulliksen Feb. 11, 1941 2,239,289 Goodhue Apr. 22, 1941 2,308,752 Hadfield Jan. 19, 1943 2,309,525 Mohr Jan. 26, 1943 2,430,310 Stratton Nov. 4, 1947 

